To work out in a rat model system optimal methods for reversal of streptozotocin-induced diabetes mellitus in rats by transplantation of syngeneic fetal pancreases. This will include the optimal gestational age of the donor, cryopreservation of the donor organ, and metabolic and immune state of the diabetic recipient. The response of the diabetic recipient will be assessed by blood glucose, urine volume and glucose and the activities of liver enzymes mediating carbohydrate and fat metabolism. Tissue typing, mixed leucocyte reactions and cryopreservation studies will be made on lymphocytes obtained from aborted human fetuses following death of the fetus in the previable period (10-20 weeks).